Broad outcomes Understand the wave nature of light and explain relationships between frequency, wavelength and speed of light Explain Planck’s quantum theory and its relevance in explaining the photoelectric effect Explain the Bohr model of the atom and its use to interpret line spectra
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Which has higher
EMR arranged in order of increasing wavelength
A laser used in eye surgery to fuse detached retina produces radiation with wavelength of 640.0 nm.
(a) Calculate the frequency of this radiation
(b) An FM radio station broadcasts electromagnetic radiation at frequency of 103.4 MHz. MHz = 106s-1
4.688 x 1014 s-1
E = h
where h is Planck’s constant, 6.63 10−34 J-s.
(a) 3.11 x 10 -19 J (b) 0.16 J (c) 4.2 x 1016 photons
Where RH is 1.096776 x 10 7 m -1, n1 and n2 are positive
integers, n2 > n1
This equation could work but not fully explained.
E = h
E = −RH
ni2Line spectra and Bohr Model
The energy absorbed or emitted from the process of electron promotion or demotion can be calculated by the equation:
where RH is the Rydberg constant, 2.18 10−18 J, and ni and nf are the initial and final energy levels of the electron.
E = −hcRH
ni2Line spectra and Bohr Model
Modified equation by Bohr of energy of hydrogen atom
n : 1 to ∞ principle quantum numbers which corresponds to different orbitals
Energy levels in the H atom from Bohr model
J ( )
E = h۷= hc/λ = −2.18 x 10-18
=6.4 The Wave Nature of Matter
mv is also referred to momentum
Calculate the velocity of neutron whose de Broglie wavelength is 500pm. The mass of the neutron is given in the table on the back of the text (1.674492716 x 10 -24 g)
= 791.88 m/s = 7.92 x 10 2 m/s
Remember: 1 J = 1 kg m 2 /s2
(x) (mv) The Uncertainty Principle
−l ≤ ml≤ l.
Observing a graph of probabilities of finding an electron versus distance from the nucleus, we see that s orbitals possess n−1 nodes, or regions where there is 0 probability of finding an electron.
This is the way the electrons are distributed among the various orbitals in the atoms
Lowest possible energy state: ground state
Without restrictions all electrons will crowd in the ground state
Orbitals are filled with increasing energy with no than two electrons per orbital
(a)Write the electron configuration for phosphorus, element 15.
(b) How many unpaired electron does a phosphorus atom posses?
(c) What do you think are valence electrons?
How is this done?_________________________
e.g. Give an example here for Na
e.g. 1s2, 2s2, 2p6in Na
What are outer shell electrons?_________________________
e.g. 3s1in Na
Lanthanide [Xe] 6s2 5d1, Cerium [Xe] 6s2 5d1 4f1
Some irregularities occur when there are enough electrons to half-fill s and d orbitals on a given row.
For instance, the electron configuration for copper is
[Ar] 4s1 3d5
rather than the expected
[Ar] 4s2 3d4.
1. Consider the system of orbitals arranged in order of increasing energy and identified by principal quantum number. Which of the following electron transitions corresponds to emission of electromagnetic radiation having the longest wavelength?
2. The valence electron configuration of an atom of an element X is 3s2 3p1 and that of an atom Y is 3s23p4. What would be the probable empirical formula for a compound of the two elements?
3. The position of four lines of the visible line spectrum of the hydrogen atom are shown below. Two lines are violet, one is red and the other is blue. Which of the following statements describes the spectrum correctly?
The lines with high energy transitions are shown to the right
The red line is shown between 450 and 500 nm
Lines with small wavelength are associated with radiation of high frequency
a. All are correct, b. 2 and 3 c. 1 and 3 d. 1 and 2, e.only 3
4. Suppose an atom has six energy levels. What would be the maximum number of lines in its emission spectrum?